الفهرس 
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Abstract
Psoriasis is a common, disfiguring, chronic, autoimmune and inflammatory disease. The most characteristic lesions consist of circumscribed, erythematous, dry and scaly plaques of variable sizes. The lesions are usually covered by silvery white scales and usually present on the scalp and extensor surfaces of the limbs. It may be produced by the interaction between both innate and acquired immunity and affected by genetic and environmental factors.
Psoriasis was previously considered as non-itchy skin disease, but nowadays there is growing evidence emphasizes on pruritus as an important complaint of psoriatic patients affecting about 60-90% of them. Pruritus has been shown to significantly impact work productivity, emotional well-being, and quality of sleep.
The pathogenesis of pruritus in psoriatic patients is still unclear. IL-17A has been suggested to have a pruritogenic role as it has been shown to participate in a number of autoimmune reactions. Interleukin-17 (IL-17) was defined as a proinflammatory cytokine produced by activated T-cells in response to stimulation through the T cell receptor.
The aim of this study was to evaluate pruritus in psoriatic patients and its possible correlation with IL17A expression in psoriatic lesions.
The present study was conducted on 60 patients with psoriasis (group A) and 20 skin specimens obtained from cases who had plastic procedures as a control (group B). The patients were clinically evaluated by PASI score and the pruritus was clinically evaluated by a questionnaire and the severity measured by VAS, then skin biopsies were taken from psoriasis lesions and H&E study for histopathological diagnosis and immunohistochemical study for IL 17 expression were done .
Clinical evaluation of pruritus in the studied cases showed that pruritus presented in 91.7% of the cases and the most common aggravating factor was stress. Moreover the most common site affected by pruritus was the lower limbs followed by the head and scalp.
Statistical analysis of IL 17 expression between cases group (A) and control group (B) showed that IL 17 is significantly higher in group (A) than in group (B).There was statistically significant positive correlation between PASI score representing the clinical severity and VAS representing pruritus severity. Moreover there was statistically insignificant correlation between the degree of IL 17 expression and grades of the VAS